Another interesting Gomphonema #glossary


Richard Carter
 

I have posted some images of Gomphonema mexicanum Grunow in Van Heurck to the "Dick's Diatoms" album.  This species has a very interesting stigma, reminiscent of that in Cymbella tumida, that makes it easy to identify.  Rather than the usual round pore, the stigma in this species is elongate, shaped like a "dash".  Just as in C. tumida, careful focussing up and down shows that the stigma is slanted, angling downward toward the central nodule.  No other member of the genus has this type of stigma, so far as I know.  The species is common across America, and seems to prefer water with elevated electrolytes.

Dick


scitech200
 

Dick,

I'm not sure that this is relevant to your specific case, but I'm beginning to notice a distinctly "different look" for species of Gomphonema depending upon the orientation of the valve about the apical axis. That is the ventral (external) view can be quite different from the internal view, especially in the central nodal area.

Rather than the usual round pore,
the stigma in this species is elongate,
shaped like a "dash".
SEM photos of G. parvulum show a round 'stigma foramen' in a ventral view, while the internal 'stigma areolus' is an elongated slot.

Best,
Keith


Richard Carter wrote:
I have posted some images of Gomphonema mexicanumGrunow in Van Heurck to the "Dick's Diatoms" album.  This species has a very interesting stigma, reminiscent of that in Cymbella tumida, that makes it easy to identify.  Rather than the usual round pore, the stigma in this species is elongate, shaped like a "dash".  Just as in C. tumida, careful focussing up and down shows that the stigma is slanted, angling downward toward the central nodule.  No other member of the genus has this type of stigma, so far as I know.  The species is common across America, and seems to prefer water with elevated electrolytes.

Dick


Richard Carter
 

Keith,

Thanks for this.  It is certainly true that the internal view of stigmata in the cymbelloid and gomphonemoid taxa (probably phylogenetic sister-groups) looks different from the external view.  Often, focusing downward on an external view will cause the appearance of a stigma to change a bit as the internal structure becomes more visible.

This seems not to account for what's going on with G. mexicanum, however.  The Diatoms of the United States website has some good images, and a description: the stigma is described as "offset", meaning that the external foramen and internal opening are not aligned along the pervalvar axis.  The amount of misalignment is somewhat variable -- I have seen some specimens in which the "dash" is barely apparent, and others in which it is quite obvious.  The great majority of specimens clearly show at least a short dash.

It is interesting to note that the stigmata of several Cymbella species look like round dots with transapical "tails" on either side.  This is definitely due to the narrow internal slit of the stigma being visible through the valve.

An excellent observation!

Dick


From: Keith Shaw
To: diatom_forum@...
Sent: Wednesday, September 12, 2012 7:57 AM
Subject: [diatom_forum] Re: Another interesting Gomphonema

 
Dick,

I'm not sure that this is relevant to your specific case, but I'm beginning to notice a distinctly "different look" for species of Gomphonema depending upon the orientation of the valve about the apical axis. That is the ventral (external) view can be quite different from the internal view, especially in the central nodal area.

> Rather than the usual round pore,
> the stigma in this species is elongate,
> shaped like a "dash".
SEM photos of G. parvulum show a round 'stigma foramen' in a ventral view, while the internal 'stigma areolus' is an elongated slot.

Best,
Keith

Richard Carter wrote:
> I have posted some images of Gomphonema mexicanumGrunow in Van Heurck to the "Dick's Diatoms" album.  This species has a very interesting stigma, reminiscent of that in Cymbella tumida, that makes it easy to identify.  Rather than the usual round pore, the stigma in this species is elongate, shaped like a "dash".  Just as in C. tumida, careful focussing up and down shows that the stigma is slanted, angling downward toward the central nodule.  No other member of the genus has this type of stigma, so far as I know.  The species is common across America, and seems to prefer water with elevated electrolytes.
>
> Dick
>




scitech200
 

Dick,

Yes, G. mexicanum definitely has a unique orientation of the stigma relative to the transapical (pervalvar) axis.
Remember us talking about the group needing to agree on a glossary of terms for consistent discussions?

Anyway, back to my favorite pursuit - I was out yesterday collecting again from the Charles River and a tributary (Stop River). With Summer coming to a close out here I figure I may as well stock up with samples for the Winter...
Of course I had to take a quick look last night and do I have some interesting specimens this time around! One site had a big population of Gomphonema and another produced what may well be the largest freshwater diatom I have ever seen - both in length and width. I'll have to calibrate an image with a 10x(!) objective, but my estimation is that the length is in the 250um range.
I tried to fit it to my understanding of Tryblionella and Nitzschia, but...

More later,
Keith



Richard Carter wrote:


Keith,
Thanks for this.  It is certainly true that the internal view of stigmata in the cymbelloid and gomphonemoid taxa (probably phylogenetic sister-groups) looks different from the external view.  Often, focusing downward on an external view will cause the appearance of a stigma to change a bit as the internal structure becomes more visible.

This seems not to account for what's going on with G. mexicanum, however.  The Diatoms of the United States website has some good images, and a description: the stigma is described as "offset", meaning that the external foramen and internal opening are not aligned along the pervalvar axis.  The amount of misalignment is somewhat variable -- I have seen some specimens in which the "dash" is barely apparent, and others in which it is quite obvious.  The great majority of specimens clearly show at least a short dash.

It is interesting to note that the stigmata of several Cymbellaspecies look like round dots with transapical "tails" on either side.  This is definitely due to the narrow internal slit of the stigma being visible through the valve.

An excellent observation!

Dick


Richard Carter
 

Keith,

I do remember our discussion of a glossary, and it's also my recollection that someone had agreed to organize one -- but I don't recall who it was now.  I would be happy to contribute definitions, and I'm sure others would do so as well.  We could add images with labels, too, and store it in the files section as a PDF or Word document.  Does the previous volunteer want to step forward again?  Failing that, are there any new volunteers?

>>relative to the transapical (pervalvar) axis.<<  These axes are different.

Hmm, largest in both length and width.  Nothing occurs to me, offhand.  Any photos forthcoming?  Sounds fascinating!

Best,

Dick


From: scitech200
To: diatom_forum@...
Sent: Thursday, September 13, 2012 6:45 AM
Subject: [diatom_forum] Re: Another interesting Gomphonema

 
Dick,

Yes, G. mexicanum definitely has a unique orientation of the stigma relative to the transapical (pervalvar) axis.
Remember us talking about the group needing to agree on a glossary of terms for consistent discussions?

Anyway, back to my favorite pursuit - I was out yesterday collecting again from the Charles River and a tributary (Stop River). With Summer coming to a close out here I figure I may as well stock up with samples for the Winter...
Of course I had to take a quick look last night and do I have some interesting specimens this time around! One site had a big population of Gomphonema and another produced what may well be the largest freshwater diatom I have ever seen - both in length and width. I'll have to calibrate an image with a 10x(!) objective, but my estimation is that the length is in the 250um range.
I tried to fit it to my understanding of Tryblionella and Nitzschia, but...

More later,
Keith


Rob Kimmich <kimmich46@...>
 

Might the glossary at Diatoms of the US [1] be useful?

-Rob

[1] http://westerndiatoms.colorado.edu/glossary


On Thu, Sep 13, 2012 at 11:13 AM, Richard Carter <rcarter68502@...> wrote:
 

Keith,

I do remember our discussion of a glossary, and it's also my recollection that someone had agreed to organize one -- but I don't recall who it was now.  I would be happy to contribute definitions, and I'm sure others would do so as well.  We could add images with labels, too, and store it in the files section as a PDF or Word document.  Does the previous volunteer want to step forward again?  Failing that, are there any new volunteers?

>>relative to the transapical (pervalvar) axis.<<  These axes are different.

Hmm, largest in both length and width.  Nothing occurs to me, offhand.  Any photos forthcoming?  Sounds fascinating!

Best,

Dick


From: scitech200 <scitech200@...>
To: diatom_forum@...
Sent: Thursday, September 13, 2012 6:45 AM
Subject: [diatom_forum] Re: Another interesting Gomphonema

 
Dick,

Yes, G. mexicanum definitely has a unique orientation of the stigma relative to the transapical (pervalvar) axis.
Remember us talking about the group needing to agree on a glossary of terms for consistent discussions?

Anyway, back to my favorite pursuit - I was out yesterday collecting again from the Charles River and a tributary (Stop River). With Summer coming to a close out here I figure I may as well stock up with samples for the Winter...
Of course I had to take a quick look last night and do I have some interesting specimens this time around! One site had a big population of Gomphonema and another produced what may well be the largest freshwater diatom I have ever seen - both in length and width. I'll have to calibrate an image with a 10x(!) objective, but my estimation is that the length is in the 250um range.
I tried to fit it to my understanding of Tryblionella and Nitzschia, but...

More later,
Keith



Richard Carter
 

Rob,

Goodness, yes!  I had not looked at this before, even though I use the site often for images.  It seems fairly complete.  Thanks for bringing it to our attention!

Dick


From: Rob Kimmich
To: diatom_forum@...
Sent: Thursday, September 13, 2012 11:53 AM
Subject: Re: [diatom_forum] Re: Another interesting Gomphonema

 
Might the glossary at Diatoms of the US [1] be useful?

-Rob

[1] http://westerndiatoms.colorado.edu/glossary

On Thu, Sep 13, 2012 at 11:13 AM, Richard Carter <rcarter68502@...> wrote:
 
Keith,

I do remember our discussion of a glossary, and it's also my recollection that someone had agreed to organize one -- but I don't recall who it was now.  I would be happy to contribute definitions, and I'm sure others would do so as well.  We could add images with labels, too, and store it in the files section as a PDF or Word document.  Does the previous volunteer want to step forward again?  Failing that, are there any new volunteers?

>>relative to the transapical (pervalvar) axis.<<  These axes are different.

Hmm, largest in both length and width.  Nothing occurs to me, offhand.  Any photos forthcoming?  Sounds fascinating!

Best,

Dick


Rob Kimmich <kimmich46@...>
 

On that page, they encourage comment on missing terms. They also appreciate knowing about typos and small editorial changes.

-Rob


On Thu, Sep 13, 2012 at 12:04 PM, Richard Carter <rcarter68502@...> wrote:
 

Rob,

Goodness, yes!  I had not looked at this before, even though I use the site often for images.  It seems fairly complete.  Thanks for bringing it to our attention!

Dick


From: Rob Kimmich <kimmich46@...>
To: diatom_forum@...
Sent: Thursday, September 13, 2012 11:53 AM
Subject: Re: [diatom_forum] Re: Another interesting Gomphonema

 
Might the glossary at Diatoms of the US [1] be useful?

-Rob

[1] http://westerndiatoms.colorado.edu/glossary

On Thu, Sep 13, 2012 at 11:13 AM, Richard Carter <rcarter68502@...> wrote:
 
Keith,

I do remember our discussion of a glossary, and it's also my recollection that someone had agreed to organize one -- but I don't recall who it was now.  I would be happy to contribute definitions, and I'm sure others would do so as well.  We could add images with labels, too, and store it in the files section as a PDF or Word document.  Does the previous volunteer want to step forward again?  Failing that, are there any new volunteers?

>>relative to the transapical (pervalvar) axis.<<  These axes are different.

Hmm, largest in both length and width.  Nothing occurs to me, offhand.  Any photos forthcoming?  Sounds fascinating!

Best,

Dick



Sarah Spaulding
 

All, 

I happened to see this post - I would be happy to add images and definitions to the Diatoms of the US glossary.

Regards, Sarah

On Sep 13, 2012, at 1:46 PM, Rob Kimmich <kimmich46@...> wrote:

 

On that page, they encourage comment on missing terms. They also appreciate knowing about typos and small editorial changes.

-Rob

On Thu, Sep 13, 2012 at 12:04 PM, Richard Carter <rcarter68502@...> wrote:
 

Rob,

Goodness, yes!  I had not looked at this before, even though I use the site often for images.  It seems fairly complete.  Thanks for bringing it to our attention!

Dick


From: Rob Kimmich <kimmich46@...>
To: diatom_forum@...
Sent: Thursday, September 13, 2012 11:53 AM
Subject: Re: [diatom_forum] Re: Another interesting Gomphonema

 
Might the glossary at Diatoms of the US [1] be useful?

-Rob

[1] http://westerndiatoms.colorado.edu/glossary

On Thu, Sep 13, 2012 at 11:13 AM, Richard Carter <rcarter68502@...> wrote:
 
Keith,

I do remember our discussion of a glossary, and it's also my recollection that someone had agreed to organize one -- but I don't recall who it was now.  I would be happy to contribute definitions, and I'm sure others would do so as well.  We could add images with labels, too, and store it in the files section as a PDF or Word document.  Does the previous volunteer want to step forward again?  Failing that, are there any new volunteers?

>>relative to the transapical (pervalvar) axis.<<  These axes are different.

Hmm, largest in both length and width.  Nothing occurs to me, offhand.  Any photos forthcoming?  Sounds fascinating!

Best,

Dick



Rob Kimmich <kimmich46@...>
 

Thank you, Sarah.


On Thu, Sep 13, 2012 at 2:16 PM, Sarah Spaulding <sarahaspaulding@...> wrote:
 

All, 

I happened to see this post - I would be happy to add images and definitions to the Diatoms of the US glossary.

Regards, Sarah

On Sep 13, 2012, at 1:46 PM, Rob Kimmich <kimmich46@...> wrote:

 

On that page, they encourage comment on missing terms. They also appreciate knowing about typos and small editorial changes.

-Rob

On Thu, Sep 13, 2012 at 12:04 PM, Richard Carter <rcarter68502@...> wrote:
 

Rob,

Goodness, yes!  I had not looked at this before, even though I use the site often for images.  It seems fairly complete.  Thanks for bringing it to our attention!

Dick


From: Rob Kimmich <kimmich46@...>
To: diatom_forum@...
Sent: Thursday, September 13, 2012 11:53 AM
Subject: Re: [diatom_forum] Re: Another interesting Gomphonema

 
Might the glossary at Diatoms of the US [1] be useful?

-Rob

[1] http://westerndiatoms.colorado.edu/glossary

On Thu, Sep 13, 2012 at 11:13 AM, Richard Carter <rcarter68502@...> wrote:
 
Keith,

I do remember our discussion of a glossary, and it's also my recollection that someone had agreed to organize one -- but I don't recall who it was now.  I would be happy to contribute definitions, and I'm sure others would do so as well.  We could add images with labels, too, and store it in the files section as a PDF or Word document.  Does the previous volunteer want to step forward again?  Failing that, are there any new volunteers?

>>relative to the transapical (pervalvar) axis.<<  These axes are different.

Hmm, largest in both length and width.  Nothing occurs to me, offhand.  Any photos forthcoming?  Sounds fascinating!

Best,

Dick




scitech200
 

Dick,

Oops, I rushed an evaluation of the structure for the G. mexicanum stigma and mixed up the description of the "offset".

To summarize, the Cartesian set of axes for a valve are indeed:
'apical' - end to end, along the length of the valve (X)
'transapical' - at a right angle (orthogonal) to X, across the width of the valve (Y)
'pervalvar' - at a right angle (orthogonal) to XY plane (Z)

So I think the offset being described for the stigma corresponds to a tilt of the canal connecting the external foramen (pore1) and internal areolus (pore2). That is, pore1 and pore2 are offset in the approximate direction of the apical axis and this introduces a tilt of the canal relative to the pervalvar axis.
Usually there is no such offset and the canal is perpendicular to the valve's XY-plane, i.e. there is no tilt relative to the pervalvar axis.

Then it follows that the canal for G. mexicanum shows in LM, with transparency of the silica valve, as a "slot" rather than a "round pore".

Details, details,... I'm envious of your proficiency in such matters! But this group can be thankful for your detailed communications as we continue to collectively keep on learning.

Best,
Keith


Richard Carter wrote:

Keith,
<SNIP>
relative to the transapical (pervalvar) axis.<<
These axes are different.
<SNIP>


Richard Carter
 

Keith,

An excellent description!  I think this is exactly right.

Dick


From: Keith Shaw <scitech200@...>
To: diatom_forum@...
Sent: Friday, September 14, 2012 6:41 AM
Subject: [diatom_forum] Re: Another interesting Gomphonema

 
Dick,

Oops, I rushed an evaluation of the structure for the G. mexicanum stigma and mixed up the description of the "offset".

To summarize, the Cartesian set of axes for a valve are indeed:
'apical' - end to end, along the length of the valve (X)
'transapical' - at a right angle (orthogonal) to X, across the width of the valve (Y)
'pervalvar' - at a right angle (orthogonal) to XY plane (Z)

So I think the offset being described for the stigma corresponds to a tilt of the canal connecting the external foramen (pore1) and internal areolus (pore2). That is, pore1 and pore2 are offset in the approximate direction of the apical axis and this introduces a tilt of the canal relative to the pervalvar axis.
Usually there is no such offset and the canal is perpendicular to the valve's XY-plane, i.e. there is no tilt relative to the pervalvar axis.

Then it follows that the canal for G. mexicanum shows in LM, with transparency of the silica valve, as a "slot" rather than a "round pore".

Details, details,... I'm envious of your proficiency in such matters! But this group can be thankful for your detailed communications as we continue to collectively keep on learning.

Best,
Keith


Richard Carter wrote:
>
> Keith,

> >>relative to the transapical (pervalvar) axis.<<
These axes are different.